Synthetic lubricating oil



United States Patent O SYNTHETIC LUBRICATING OIL Walter W. Gleason,Roselle, William E. Lifson, Union, and Elfried F. H.Pennekamp,Westfield, N.J., assignors to Esso Research and Engineering Company, acorporation of Delaware No Drawing. Continuation of application SerialNo.

316,732, October 24, 1952. This application December 28, 1955, SerialNo. 555,750

4 Claims. (Cl. 25249.8)

This invention relates to synthetic lubricating compositions andparticularly to synthetic lubricating oils usefulfor lubrication at lowand high temperatures. More particularly, the invention relates tosynthetic lubricating oils which have outstanding utility at low andhigh temperatures and which comprise blends of a branched syntheticlubricating oils are'characterized by lower volatility, higher viscosityindices, and lower pour points than mineral oils of a correspondingviscosity level.

Lubricants possessing such properties are of special value in thelubricating of'moving parts such as combustion turbines, particularlythose of the prop jet and turbojet type for aircraft. Mineral oillubricants containing added viscosity index improvers, pour pointdepressors, or other highly non-volatile additives are undesirableforuse in such engines because of it their tendency to leave a'residuewhich accumulates and interferes with the operation of the turbine. Yetit has been found that these additivematerials must be added to mineraloils to give them extreme pressure resistance and viscositycharacteristics essential for operating at the extremetemperaturetditferentials experienced. The synthetic lubricants of theester type are especially adaptable for use under such conditions sincethese lubricants contain no additive materials and have a desirablecom-' bination of low.volatility, low pour points, and high viscosityindices. 1

With the continued development of aircraft engines Patented Jan. 12,1960 t 2 t (1,) A1 branched chainalcohol ester of a dibasic acid; (2)Acomplex esteriand (3) Tricresyl phosphate.

It is to be understood, of course, that other additive materials may beadded to the basic blend to further enhance the properties of theblend.For instance, oxidation inhibitors, such as phenothiazine, may be added;viscosity index impr'overs or pour depressants may be incorporated intothe finished lubricant. In general, however, for reasons pointed outabove, it is desirable to keep the amount of additive materials to aminimum and only in circumstances requiring special propertieswilltthese additive materials be included in the finished product.

' A more detailed description of the component parts of the compositionsof invention is set out below.

THE BRANCHED CHAIN DIESTER The dibasic acid which is fully esterified toform the diester portion of the lubricating oil blend may be selectedfrom sebacic and adipic acid. These acids are well'known in the art andneed no further description.

The branched chain alcohol which is used to form the diester of the acidis selected from a group of alcohols which contain from 6 to 16 carbonatoms in branch chain configuration. It is essential that there be somedegree of branching in the carbon chain of the alcohol, and, withinlimits, the higher the degree of branching the more satisfactory thelubricant. Alcohols such as ethylbutyl, ethylhexyl and other well knownbranch chain alcohols are operable.

One group of alcohols that have recently become commercially availableand that answer the requirements for the esterifying alcohol are theso-called 0x0 alcohols. These alcohols are preferred and arecontemplated in the preferred embodiment of this invention.

The Oxo alcohols are prepared by the catalytic reaction of an olefinwith carbon monoxide and hydrogen. The reaction, called Oxo synthesis,occurs at temp peratures in the order of 300 F. to 400 F. at pressuresin the range of about 1000 to 3000 psi. In the presence of :a suitablecatalyst, ordinarily a heavy metal carbonyl, such ,as ,cobaltcarbonyl,there is formed an aldehyde, which is subsequently hydrogenated to aprimary alcohol. This process was first developed in Germany andisdescribed in US. Patent No. 2,327,066, issued to Roelen in 1943..

In general, the oxygenated group in a product from an olefin by the 0x0process is thought of as becoming attached to an unsaturated carbonwhich holds at least designed to operate at peak eificiency at highaltitudes.

it has been found that there also exists a problem of lubricity or loadcarrying capacity. It is with this problem of incorporation of desirableviscosity properties with lubricity or load characteristics which may betermed extreme pressure resistance in a synthetic oil blend that thisinvention is concerned.

It has now been found, and forms the object of this invention, that asynthetic lubricating composition having outstanding high and lowtemperature characteristics and outstanding extreme pressure resistancemay be prepared by blending with a branched chain alcohol ester of adibasic acid, a minor amount of a complex ester and a minor amount oftricresyl phosphate. The proportions of the resulting blend are criticaland will be specifically illustrated in detail below.

As was stated above, there are three distinct components in thesynthetic lubricating oil composition of this invention. They are:

one hydrogen atom. In those cases where the carbon monoxide attacks asaturated carbon atom, it must be assumed either that that carbon hasbecome unsaturated prior to reaction by a shift of a hydrogen atom, orthat the attack is directly on a carbon atom that is truly saturated.For example, 2-butene has been reported to give -1-pentano1 andZ-methylbutanol in equal quantities,

a result that cannot be explained on the simple basis' streams andprocesses for their conversion to liquid copolymers have been worked outby the art. One such process, known as UOP polymerization, consists ofpassing the olefin-containing stream in liquid, phase in contact with anacid catalyst comprising phosphoric acid impregnated on kieselguhr.Other acidic catalysts, such as phosphoric acid or copper phosphateimpregnated on silica gel, sulfuric acid, Friedel-Crafts catalysts,activated clays, silica-alumina, copper pyrophosphate, etc., may beused. Suitable conditions when employing phosphoric acid catalysts ofthe UOP type are temperatures of 300 F. to 500 F., pressuresfrom 250 to5,000 p.s.i., and feed stocks comprising refinery streams containingpropylene and mixed butylenes. Suitable feed stocks, for example, maycontain from 15" to 60 mol percent propylenes, from 0.5 to 15 molpercent butylenes, and from 0.1 to 10 mol percent isobutylene, theremaining being saturated hydrocarbons. Other suitable feed stocks arethe dimer and trimer of'isobutylene.

Of the x0 alcohols operable, those alcohols having from 6 to 16 carbonatoms are preferred. They are prepared from olefin polymers orcopolymers having from to carbon atoms. In, preparing these Oxoalcohols, the desired olefin fraction is. segregated from the crudeolefin polymer product by fractionation.

As was stated above, the 0x0. alcohols are especially desirableesterifying alcohols because of their, optimum degree of branching. Forexample, the following. table shows the structure and percentagecomposition of a C Oxo alcohol prepared from a C olefin stream which hadbeen fractionated from the products obtained by the phosphoric acidpolymerization of refinery gas streams containing propylene and mixednand isobutylenes.

It will be noted that Oxo alcohols derived from the olefinsproduced by C43 polymerization are mostly methyl substituted.

Of the preferred Oxo alcohols operable as the acid esterifying, agent,that-is, those Oxo alcohols having from 6 to l6,car b on atoms,especially preferred are'those OX0 alcohols having from 6 to 9 carbonatoms, that is, the Oxot alcohols prepared from olefins having fr om- 5m8- carbon atoms. Specifically, they. are the=C 0x0 alcohol, gllie gioxo alcohol, the C Oxo alcohol, and the C Oxo 4 THE COMPLEX ESTER Thesecond component of the synthetic lubricating compositions of thisinvention is generally known to the art as a complex ester. Thismaterial may be generally described as being the reaction product of twoor more of the following compounds: 7

(l) Monohydric alcohols (2) Monobasic acids (3), Dibasic acids (4)Glycols (5) Polyhydric alcohols (6) Polybasic acids where at least onepolyfunctional alcohol and at least one polyfunctional. acid areemployed.

These complex esters may be grouped under the following types:

Type I.--M'0n0basic acid-glycol-dibasic acid-glycolmonobasic acid Thiscomplex ester, may beconsidered to have the following structuralformula:

wherein. R and R are the alkyl radicals of the monobasic acids; R and Rare the alkyl radicals of the glycols, and R isthe alkyl radical of the:dibasic acid.

The esters of this type may be prepared by admixing the calculatedamounts of the various compounds and carrying out a straightforwardesterification reaction. The reactionconditions are continued-with anoccasional sample of the product being tested for acidity until the minimum acidity is attained.

Type II;-Alcoholedibasic acid glycol-dibasic acid-alcohol This ester,especially preferred among all the complex esters, has the followinggeneral formula:

it t

whereinR; and R are the combiningradicals of the alcohol, R and,.R arethe alk-ylraclicalsof the dibasic acid, and R isthe a-lkyl radical of.the glycol.

These: esters are prepared as those of Type I above but preferably theyare prepared by first forming the half-ester of the dibasicacid'andtheglycol, and subsequently reacting two mols of, such half-ester. withtwo mols of the alcohol;

Type IlI.Alc0hol-dibasic acid-glycol-monobasic acid This ester may berepresented by the followingformula:

Type I V.-Monobasic acidglycol-dibasic acid-glycolmonobasic acid Y Thesesynthetic complex esters may be said to have the general formula; 1

wherein R and R are the alkyl radical of the monobasic acid, R and R arethe alkyl radicals of the glycol, and R is the alkyl radical of thedibasic acid.

It will be noted that these esters are of the same formula as thoseappearing above under Type I, except that this type is prepared byreacting a monobasic acid with a glycol under such conditions that ahalf ester is formed, and reacting two mols ofsuch ester with one mol ofa dibasic acid. 1 r

The alcohols used in forming the esters set out above include thefollowingwmethyl, ,ethyl n-butyl, ;n,-hexy1, n-octyl, 2-ethylhexyl,cetyl, oleyl, the ether alcohols formed by the reaction of ethyleneoxide or;propylene 1 oxide with aliphatic alcohols, etc. One especiallysuitable group of alcohols are the 0x0 alcohols described in detailabove.

Among the monobasic acids which maybe employed in the preparation of thecomplex esters, the following may be listed as illustrative:- acetic,propionic, butyric,

valeric, capric, caprylic, pelargonic, lauric, palmitic, stearic, oleic,beta-methoxypropionic, beta-ethoxypropi-' glycol, triethylene glycol andthe polyethylene glycols of the formula:

HO(CH CH O),,CH CH OH sulfur atoms in thio-ether linkages include suchcompounds as thiodiglycol and 1,2-bis(Z-hydroxyethylmer-' capto) ethane.There also may be used glycols containing both oxygen and sulfur insimilar linkages, such a compound is bis-2-(2-hydroxyethoxy) ethylsulfide.

The preferred embodiment contemplates an ester of Type II, for instance,one that is prepared by reactingrtwo p wherein n is 1 to 26 may be used.Glycols containing mols of a branched chain alcohol of from 6, to 10carbon atoms with two mols of a half ester of a dibasic acid, such assuccinic, glutaric, adipic, pimelic, suberic, azelaic, or sebacic acid,and one mol of a glycol such as polyethyleneglycol. Specificallypreferred is the reaction product according to the above procedure of2-ethylhexanol,

adipic or sebacic acid, and a polyethylene glycol of a molecular weightof about 200.

New design turbo-jet and turboprop engines fea'. turing high compressionratios and increased poweroutput have forced temperatures upwardandhaveincreas'd the load on gears and bearings. Oil cooling has alsobecome a problem since bearing temperatures in excess of These factorssubject the;

450 F. are not uncommon. lubricant to extremely severe conditions withregard to high temperature performance and load handling ability inaddition to the ordinary low temperature requirements. Lubricantsdesigned for these engines,.therefore, must exhibitan outstandingcombination of physical and chemical properties.

As the temperature increases the lubricant tends to thin out or decreasein viscosity. It is essential, however, that at the high temperatureexperienced the lubricant retain sufficient viscosity to furnish thelubricity necessary for decreasing friction. It has been found that inthese new design engines, the viscosity of the oil at 210 F. and at 100F. should be at least 3.0 and 11.0 centistokes respectively.

The load carrying ability of lubricants designed for these new uses mustbe adequate to properly lubricate the main antifriction bearings at highspeeds. This is particularly true for the reduction gear assembly foundin turbo prop engines. Exhaustive tests have shown that the loadcarrying capacity for a lubricantfor this use should be such as toresult in a Shell 4-Ball seizure point of about 70 kilograms and a weldpoint of about 120 kilograms, both values given being minimum values.The explanation of the Shell 4-Ball test is set out in detail below.

In order to prevent excessive oil consumption, the lubricant mustpossess a sufficiently low volatility. The ASTM flash point is used as ameasure of volatility and it has been found that lubricants possessingflash points in excess of about 390 F. have been found to be satisfacoryin this respect.

The viscosity of the oil at the minimum starting temperature of theengine must be sufliciently low so as toprevent serious reduction in theoil flow rate. The maximum viscosity of the oil which can be pumped inadequate quantity has been found to be about 14,500 centistokes at -65F.

It is generally recognized, therefore, that in order to furnishsatisfactory lubrication of the new design turbo jet and turbo propengines that a lubricant should have a viscosity at 210 F.'of at least3.0 centistokes, a viscosity at 100 F. of at least 11.0 centistokes, aviscosity at 65 F. of no more than 14,500 centistokes, and a loadcarrying capacity sufficient to obtain a Shell 4-Ball Extreme Pressuretest seizure load of about 70 kilograms and a weld load of 120kilograms.

In order to obtain the combination of properties referred toabove, therelative amounts of the three combe complied with as follows:

The lubricating composition must be composed of about 2% to 10% byweight of tricresyl phosphate and about 98% to by weight ofa blend ofesters, said blend consisting of from about 85% to about by volume ofthe dibasic acid ester and from about.5% to about 15% by volume of thecomplex ester.

The tricresyl phosphate, the load carrying additive, must be present inamounts between about 2% and 10% by weight based on the weight of thetotal composition. Increasing the complex ester and the tricresylphosphate content above the specified limits produces no significantbeneficial efiect on load carrying ability'an'd increases the lowtemperature viscosity beyond the level required for low temperatureengine starting and operability. Decreas ing the complex ester ortricresyl phosphate content will be reflected by unsatisfactory loadhandling ability.

The-testing procedure utilized for determination of extreme pressurecharacteristics is the well-known 4-ball, extreme pressure testdeveloped by the Shell Development Company. This test procedure is knownto the art as the Shell 4-Ball Test.

Briefly, the test consists of the following: .3 stainless steel balls infixed relation are contacted by a 4th'ball which is rotated at highspeeds. The arrangement is such that the 3 stationary balls are eachcontacted by the 4th rotating ball. By mechanical linkage, extremepressures are placed on the points of contact through the rotating ball.contact. As pressure increases, it has been noted that the first pittingof the contacting surfaces occurs when the pressure is sufiicient toforce the lubricant from between the metal contacting surfaces. Thisinitial pitting or The lubricant to be tested surrounds the points of 7scoring, an actual seizing of the metal of the surfaces, is called theseizure point. As pressure is increased, a point is reached at which.the metal surfaces actually weld and the 4 balls become one unit. Thispoint is referred to as the weld poin It is to be seen that an increasein the seizure point and the weld point indicates an increase in thelubricity of the test material. Results of the test are reported inkilograms.

Various combinations of the components of the lubricating oilcompositions of this invention were prepared. The viscosity propertieswere measured and the compositions were subjected to the 4-Ball ExtremePressure Test. In the first series of tests, the diester used was a di-COxo adipate. The complex ester used was the reaction product of 2 molsof a half ester of sebacic acid and 2 mols ethylhexanol with one mole ofa polyethylene glycol maximum amount of'the complex ester that can beadded for optimum results considering both viscosity and load carryingcapacity. Greater amounts of the complex ester do not improve thecomposition. The data also show that amounts of the tricresyl phosphatein excess of about 10% are unnecessary. It is interesting to note that acombination of 5% of the complex ester and 5% of tricresyl phosphategives an extreme pressure test result which is better than would'bepredicted from the addition' of 10% of either component.

In a second series of lubricants, combinations of the same complex esteras-used above with di-Z-ethylhexyl sebacate were prepared and inspected.The data show the outstanding advantage of combinations of thecomplexester and tricresyl phosphate within the stated limits and areset out in TableII below:

TABLE II Physical data on synthetic oil compositions [Baseo11D1-2-ethylhexyl sebacateJ Makeup of Ester Shell 4-Ball E. P.Viscosity in Centistokes Blend Test, Kg. Load- Desired Properties Wt.Per- Desired Properties cent Tri- Lubricant N0. cresyl Vol. Per- Vol.Per- Phosphate At At At cent cent Selz., Weld, F 100 F., F., DiesterComplex (min) 120 (min.) 3 0 (mil?) 11.0 14,500 Ester (min) (max) havinga molecular weight of about 200. Results of the tests on thesecompositions are set out in Table I below:

TABLE I A third series of lubricating compositions were prepared usingas a base oil a dl-C7 Oxo adipate. Combina- Physical data on syntheticoil compositions [Base Oil-Di-Cs 0x0 adipate] Makeup of Ester Shell4-Ball E. P. Viscosity in Gentistokes- Blend Test, Kg. Load- DesiredProperties Wt. Per- Desired Properties Lubricant No. cent Tricresyl Vol.Per- Vol. Per- Phosphate Seiz., Weld, 210 F., 100 F., 65 F.,

cent cent 70 (min) 120 (min.) 3.0 (min) 11.0 14,500 Diester Complex(min.) (max.)

Ester 95 5 0 45 120 3. 03 11. 18 8, 349 95 5 3 70 130 3. 07 11. 36 10.95 5 5 70 130 3. 08 11. 43 10, 815 95 5 10 60 130 3. 11 11. 91 14, 11490 10 0 .45 140 90 10 3 70 140 3. 28 12. 23 12, 700 90 10 5 75 140 3. 2812.23 13, 400 90 10 10 70 140 90 10 20 70 140 65 35 0 65 140 10. 26 53.6 Solid 60 40 5 140 60 40 10 100 140 35 65 0 60 140 4. 62 18. 78 38, 72435 65 3 75 140 4. 63 18. 84 42, 766 35 65 5 85 140 4. 61 18. 99 48, 67685 65 10 80 140 4. 54' 19. 22 50, 836 35 e5 20 so 140 p r 0 100 0 65 14010. 26 53. 60 Solid 0 100 3 80 140 10. 10 53. 10 Solid 0 100 5 10. 0152. 75 Solid 0 100 10 120 130 9. 76 52. 49' Solid An examination of thedata of Table I above shows that the incorporation of the complex esterin the lubricant increases the viscosity and the load carrying capacityof the oil. These data also show that about 10% is the tions of thisbase oil with the complex ester and tricresyl phosphate show anoutstanding advantage for the use of the compositions of this invention.The data are reported 75 in Table III'below:

TABLE III Physical data on synthetic oil composition [Base oil-C1 0x0adlpata] Makeup 01 Ester Shell 4-Ball E. P. Viscosity ln Centlstokes-Blend Test, Kg. Load- Desired Properties Wt. Per- Desired Propertiescent Tri- Lubricant No. cresyl Vol. Per- Vol. Per- Phosphate At At Atcent cent Sela, Weld, F 100 F., 65 F., Diester Complex 70 (min.) 120(min.) 3 0 11.0 14,500 Ester t (ruin.) (max) The lubricatingcompositions of the instant invention have been found to be compatiblewith additive materials that are useful to enhance certain properties ofa lubricant. For instance, it has been found that certain oxidationinhibitors such as polynuclear phenols, alkylated phenols,phenothiazine, alkylated phenothiazine, etc., enhance oxidationstability of the base oil whenincorporated in amounts varying from about0.1 to 2.0 weight percent. Detergent inhibitors such as petroleumsulfonates, or metallic salts of petroleum sulfonates, such as thesodium, zinc, magnesium, barium salts, etc., may also be blended withthe base composition. These inhibitors are found to be most advantageousin amounts varying between about 0.1 to about 5.0 weight percent. Rustinhibitors such as the po'lyhydroxy esters, represented by sorbitanmonooleate and pentaerythritol monooleate, may be blended into thefinished composition in amounts varying between 0.1 and 5.0 weightpercent. From 0.1 to 2.0 weight percent of lecithin may be added as acorrosion inhibitor. Foam depressants such as silicone fluids may beadded in amounts up to about 0.1 weight percent.

The compositions of invention may also be fortified against a tendencyto cause rusting by incorporation of minor amounts of mineral oil. Fromabout 5.0 to about 15.0 weight percent may be added to the finished oilto accomplish this.

To summarize briefly, this invention has as its object lubricating oilcompositions which have outstanding properties at both high and lowtemperatures and have extreme pressure-resisting characteristics whichmake them especially suitable for use in jet engines. These newlubricating compositions are prepared by blending within certainspecific limits (1) an ester of a dibasic acid in figuration andcontains from 6 to 16 carbon atoms, (2)

a complex ester formed by the interaction of a glycol, a-

dibasic acid, and a branched chain alcohol having from 6 to 16 carbonatoms, and (3) tricresyl phosphate. It is within the concept of thisinvention to add to the blended lubricant other materials such asphenothiazine, viscosity index improvers, pour point depressants, otherextreme pressure resistants, detergent inhibitors, oxidation inhibitors,rust inhibitors, sludge dispersants, etc. In the preferred embodiment ofthis invention, from 95% to 85% by volume of the diester is blended withfrom 5% to by volume of the complex ester, and from 98% to 90% by weightof this blend is mixed with from 2% to 10% by weight of tricresylphosphate. Especially pre ferred as the esterifying alcohols for boththe diester and the complex ester are the alcohols produced from the 0x0process. Especially preferred is a blend of from 85% to 95% by volume ofa O; or C branched chain alcohol ester of a dibasic acid with from 5% to15% by volume of a complex esterformed by reacting 2 mols of a halfester of adipic or sebacic acid, and 2-ethylhexyl alcohol with one molof a polyethylene glycol having a molecular this blend being'mixed withfrom 2% to 10% by weight of tricresyl phosphate.

This case is a continuation of US. Serial No. 316,7 32 filed October 24,1952, now abandoned, for the same inventors.

What is claimed is:

1. A synthetic lubricating composition suitable for the lubrication ofmoving parts of combustion turbines in aircraft engines over a range oftemperatures of from about 450 F. to about -65 F. under conditions ofextreme pressure which comprises a synergestic mixture of about 2.0 to10.0 percent by weight of tricresyl phosphate and from 98.0 to 90.0percent by weight of a blend of esters, said blend of esters consistingessentially of from 90.0 to 95.0 percent by volume of a diester and fromabout 10.0 to 5.0 percent by volume of a complex ester, said diesterbeing formed by esterifying a branched chain alcohol with a dibasic acidselected from the group consisting of sebacic and adipic acids and saidcomplex ester being formed by esterifying 1 mol of a polyethylene glycolhaving a molecular weight of about 200 with 2 mols of a half ester ofsebacic acid and 2-ethyl hexanol, the numerical ratio of the vol.percent of said complex ester in said blend to the wt. percent of saidtricresyl phosphate in said composition is in the ratio of 1:1 to 2.5:1.

2. A synthetic lubricating composition according to claim 1 wherein saiddiester is formed by esterifying 1 mol of the adipic acid with 2 mols ofa mixture of isomeric primary branched chain alcohols having 8 carbonatoms, said mixture of alcohols having been prepared by subjecting anolefin having 7 carbon atoms to the action of carbon monoxide andhydrogen in the presence of a carbonylation catalyst at a temperature ofabout 300 F. to about 400 F. and a pressure of about 1000 to about 3000pounds per square inch.

3. A synthetic lubricating composition according to claim 1 wherein saiddiester is formed by esterifying 1 mol of sebacic acid with 2 mols of2-ethyl hexanol.

4. A synthetic lubricating composition suitable for the lubrication ofmoving parts of combustion turbines in aircraft engines over a range oftemperatures of from about 450 F. to about 65 F. under conditions ofextreme pressure which comprises a synergistic mixture of about 5.0 wt.percent of tricresyl phosphate and about 95.0 wt. percent of a blend ofesters, said blend consisting essentially of 95.0 vol. percent of adiester formed by esterifying 1 mol of adipic acid with 2 mols of amixture of isomeric primary branched chain alcohols having 8 carbonatoms, said mixture of alcohols having been prepared by subjecting anolefin having 7 carbon atoms to the action of carbon monoxide andhydrogen in the presence of a carbonylation catalyst at a temperature ofabout 300 F. to about 400 F. and a pressure of about 1000 to about 3000pounds per square inch, and 5.0 vol. percent of a complex ester, saidcomplex ester havmg been prepared by esterifying 1 mol of a polyethylene1 1 glycol having a molecular weight of about 200 with 2 2,628,974 molsof a half ester of sebacic acid and 2-ethyl hexanol. 2,639,266.2,729,665 References Cited in the file of this patent 2 753 975 UNITEDSTATES PATENTS 5 2,285,855 Downing et a1 June 9, 1942 2,410,608 MorganNov. 5,, 1948 2,499,984 Beavers et a1 Mar. 7, 1950 12 Sanderson Feb. 17,1953 Dilworth et a1, May 19, 1953 Buckmann Jan. 3, 1956 Cottle et a1Aug. 14, 1956 OTHER REFERENCES Ind. & Eng. Chem. vol. 42, No. 9, pp.1841-1847. Lubrication Engineering, August 1952, pp. 177-200,

1. A SYNTHETIC LUBRICATING COMPOSITION SUITABLE FOR THE LUBRICATING OFMOVING PARTS OF COMBUSTION TURBINES IN AIRCRAFT ENGINES OVER A RANGE OFTEMPERATURES OF FROM ABOUT 450*F. TO ABOUT -65*F. UNDER CONDITIONS OFEXTREME PRESSURE WHICH COMPRISES A SYNERGESTIC MIXTURE OF ABOUT 2.0 TO10.0 PERCENT BY WEIGHT OF TRICRESYL PHOSPHATE AND FROM 98.0 TO 90.0PERCENT BY WEIGHT OF A BLEND OF ESTERS, SAID BLEND OF ESTERS CONSISTINGESSENTIALLY OF FROM 90.0 TO 95.0 PERCENT BY VOLUME OF A DIESTER AND FROMABOUT 10.0 TO 5.0 PERCENT BY VOLUME OF A COMPLEX ESTER, SAID DIESTERBEING FORMED BY ESTERIFYING A BRANCHED CHAIN ALCOHOL WITH A DIBASIC ACIDSELECTED FROM THE GROUP CONSISITING OF SEBACIC AND ADIPIC ACIDS AND SAIDCOMPLEX ESTER BEING FORMED BY ESTGERFYING 1 MOL OF A POLYETHYLENE GLYCOLHAVING A MOLECULAR WEIGHT OF ABOUT 200 WITH 2 MOLS OF A HALF ESTER OFSEBACIC ACID AND 2-ETHYL HEXANOL, THE NUMERICAL RATIO OF THE VOL.PERCENT OF SAID COMPLEX ESTER IN SAID BLEND TO THE WT. PERCENT OF SAIDTRICRESYL PHOSPHATE IN SAID COMPOSITION IS IN THE RATIO OF 1.1 TO 2.5:1.